Example embodiments disclosed herein may relate to apparatuses for use in fabricating semiconductor devices. In particular, example embodiments disclosed herein may relate to a filament member, an ion source and an ion implantation apparatus.
Ion implantation is a process of injecting impurities, for example, P-type or N-type impurities, for example boron (B), aluminum (Al), and indium (In), or, antimony (Sb), phosphorous (P), and arsenic (As), which may be controlled in a plasma ionic condition, into a pure silicon (Si) wafer to produce a device with required conductivity and resistivity. Ion implantation techniques have been widely used to manufacture semiconductor devices, because controlling the concentration of impurities injected into a wafer may be easier.
An apparatus used for ion implantation may have an ion source for generating ion beams. FIG. 1 is a sectional view schematically illustrating a conventional ion source 900. Referring to FIG. 1, the ion source 900 may have an arc chamber 920 including a port 922 for introducing source gas thereinto and an ion beam outlet 924 through which ions, for example, positive ions may be supplied thereinto. The arc chamber 920 may contain a filament 940 for emitting thermions. When connected with a power supply, the filament 940 may heat to a desired temperature to emit electrons. The emitted electrons may collide with gas molecules in the arc chamber 920 to ionize the gas molecules. During this process, gaseous plasma with various ions and electrons may be generated. The generated ions may be emitted through the ion beam outlet 924 and implanted into a wafer.
The filament 940 may be coiled as illustrated in FIG. 1. Each end of the filament 940 may be connected to a cathode and an anode. Current may flow from the anode to the cathode through the filament 940. When current flows, a thermionic current induced at a middle of the filament 940 may cause the filament current to be larger nearer to the cathode than the anode. As a result, the amount of hot electron emission may become unbalanced over the filament 940, wherein more thermions may be emitted near the cathode than the anode.
Positive ions generated in a region adjacent to the filament 940 may be incident on the filament 940. Those positive ions may collide against the filament 940, which may cause a sputtering etch effect on the filament 940. The sputtering etch effect may degrade the filament 940, resulting in a short, and may shorten the life span and/or endurance of the filament 940. Degradation of the filament 940 also may cause an increase in preventive maintenance cost and/or repair.
The sputtering etch effect may be higher when the positive ions are incident on the surface of the filament 940 at an angle of around 30° through 60°. Accordingly, the filament 940, may be shaped as a wire, for example a pig's tail, as shown in FIG. 2. The majority of the positive ions may collide with the filament 940 at an angle of around 30° through 60°.
Further, as aforementioned, because the thermions emitted from the filament 940 may be more abundant around the cathode, more positive ions may be generated in regions adjacent to the cathode. Thus, positive ions applied onto the filament 940 may increase around the cathode, increasing the sputtering etch effect at those regions thereof.
Therefore, if the filament is shorted due to the sputtering etching effect, the ion implantation equipment may have to be shut off to replace the shorted filament.
Moreover, using the conventional filament, electrons emitted from the filament may partially discharge and collide with a sidewall of the arc chamber, thereby damaging the arc chamber.